In a component mounting line for mounting electronic components on a board, screen printing is used as a method of supplying paste for bonding the components such as cream solder to the board. In the screen printing, by performing a squeegeeing operation of making a screen mask which is provided with pattern holes corresponding to printing positions of the paste to abut against the board, supplying paste onto the screen mask and sliding a squeegee, the paste is printed on the board through the pattern holes. In order to print the paste correctly in the screen printing, it is necessary to align the board with the screen mask correctly.
The board alignment is performed by imaging and recognizing the positions of recognition marks that are generally provided on the board and the screen mask, respectively, with a camera. At this time, because the position reference of the coordinate system when the board is imaged is different from that of the coordinate system when the screen mask is imaged, it is necessary to obtain the position reference data which identify the positional relationship between these coordinate systems. Therefore, traditionally, a screen printing device is known which includes a calibration processing function of obtaining the position reference data between the coordinate systems by imaging the board and the screen mask (for example, refer to a patent document 1). In the related art shown in this patent document, a construction example is shown which images a screen mask and a board with a single camera of an optical system including a prism, and imaging lights incident from the screen mask and the board in upwards and downwards coaxial directions are recognized by dividing the imaging field of the camera into a top half and a bottom half. By adopting such a construction, both the screen mask and the board can be recognized with the single camera, and it becomes possible to simplify the construction of the recognizing device.